This project involves the application of the SSES methodological approach to the study of basic cognitive, neuropsychological and psychopathological processes and their modulation by the environment. As part of this project we collaboratively provide statistical expertise and carry out innovative statistical analyses for other intramural research groups. One such collaboration is a longstanding one with Dr. Jordan Grafman (Chief, Cognitive Neuroscience Section NINDS) centering on the longitudinal Vietnam Head Injury Study (VHIS). In collaboration with Dr. Grafman and Dr. Salazar, we have used Structural Equation Modeling (SEM) based mixture modeling to categorize the VHIS head injured Vietnam veterans into statistically coherent groups based on the patterns of their brain injuries. We have also used SEM to investigate the factorial structures of both memory and cognitive functioning in these veterans. This year we have provided evidence of how the different patterns of brain injury of these statistically coherent groups of veterans affect the ways in which their memory and cognitive functioning differs from that of the non-brain injured controls in theoretically meaningful ways. This year we also collaborated with Dr. Grafman's group in a survey study for which his group is currently collecting data on the interactions between the nature of the veterans' head injuries and how social-structurally determined environmental conditions affect psychological and psychosocial functioning. This year we have also started a collaboration with Dr. Dennis Murphy, (Chief, Laboratory of Clinical Science, NIMH). The first goal of this collaboration is to use SEM to reliably ascertain the underlying factorial structure of Obsessive Compulsive Disorder (OCD) symptomatology. A second goal is to use the patterns of interrelations among these factors to distinguish different sub groups of OCD. Our initial analyses suggest that we will be successful in achieving these two goals. We eventually hope to be able to link membership in these different symptom-based groups to differences in heredity and comorbidity. This year we have also completed analyses on data from a number of experimental psychological studies previously carried out by the SSES on a sample of normal and schizophrenic individuals. These analyses have focused on task context, and how the performance of schizophrenic individuals is negatively affected by complex task demands, stimulus-response incompatibility, and by a marked difficulty in dealing with the temporal aspects of context. Taken together with the findings of earlier experiments carried out by the SSES and other investigators, this pattern of results suggests the existence of temporal mini-gaps in schizophrenic individuals? cognitive functioning. Such mini-gaps would seem to be related to Andreasen?s concept of schizophrenic cognitive dysmetria- a loss of smooth continuous function that Andreasen sees as resulting from disruption in the cortico-cerebellar-thalamic-cortical circuit.